Four hundred fifty (450) MHz electromagnetic fields (EMFs, 0-5 mW/sq. cm.), unmodulated and amplitude modulated by extremely low frequency (ELF) sine waves will be used in the following studies: 1) Neurochemistry and electrophysiology (mammalian tissue). These studies will assess the effects of fields on ionic binding, neurotransmitter release and electrophysiological activity of intact and isolated brain tissue (rat hippocampal slices, intact cat cerebral cortex and synaptosomes from rat cerebrum). Extracellular microelectrode recording from brain slices will be correlated with neurochemical data obtained from tissue during identical field exposures. 2) Developmental studies. Possible effects of EMF on the maturation of the rat hippocampal formation will be assessed. Techniques will be developed to culture hippocampal slices from neonatal state to two weeks old. Functional maturation of the tissue will be studied with extracellular microelectrode recording. Maturation of synapses and patterns of synaptic connections will be studied by electron microscopy. 3) Flurorescent microscopy. 3) Fluorescent microscopy of cerebral tissue. We will examine the field sensitive calcium binding sites in hippocampal tissue, using microfluorometry in an attempt to provide direct evidence of field-membrane interactions. 4) Electrophysiology (invertebrate). Intracellular recordings from pacemaker neurons of the isolated Aplysia abdominal ganglion will study the changes in neuronal excitability during and after irradiation by the EMFs that will permit determination of interaction mechanisms and parameters of the effective field levels and modulation frequencies. 5) Behavior. In these studies in rats, the influence of EMFs with differing modulation frequencies and power levels on performance on a Fixed-Time schedule of reinforcement and the discriminative properties of EMFs with differing power levels and modulation frequencies will be tested with and without CNS active substances. 6) Mathematical models. It is proposed to derive an explicit system of partial differential equations which may be used to model observed calcium fluxes in cerebral tissue.